This project will determine whether the well-described paradigm of the model-tracing Intelligent Tutoring System can be adapted to create a multimedia, knowledge-based, medical training system in Pathology. Intelligent Tutoring Systems (ITS) are computer-based systems that provide individualized instruction by incorporating models of expert performance and dynamically building a unique student model for each user. ITS can be highly effective in systems that simulate real-world tasks, enabling students to work through case based scenarios as the ITS offers guidance, points out errors and organizes the curriculum to address the needs of that individual learner. We propose to implement and evaluate such a system in Dermatopathology - the pathology of skin disease. The methodology to be used is grounded in a theory of human skill acquisition that has been widely tested. We will utilize a rule-and-frame expert model guided by our previous work describing the development of visual diagnostic expertise in Pathology. The system will incorporate a Virtual Microscope simulation, and access a library of whole-slide digital images. System development will be accompanied by a set of formative evaluations in which we will specifically compare alternatives for maximizing educational impact, and explore the design issues most critical for adapting the ITS paradigm into a medical domain. Key areas of research during the formative evaluation include: (1) examination of immediate feedback versus post-case critiquing, (2) evaluation of alternative methods for student modeling, and (3) the testing of interfaces for reifying diagnostic problem solving. During the final years of the project, our efforts will be directed towards summative evaluation of the effect of the composite system, in laboratory and field studies.